LONG TERM BIODEGRADATION OF ELASTOMERIC MATERIALS

该产品具有优异的物理和化学性能， 聚氨酯（PU）与其生物相容性相结合， 广泛应用于生物医学领域。 在过去的十年里， 当一些聚氨酯产品出现生物稳定性问题时， 起搏器电极导线显示出在 人类本实验室目前的研究旨在从根本上 了解PU弹性体的生物相容性和生物稳定性， 导致了一个假设，细胞/聚合物反馈控制体内 生物降解 为了证实和/或修改假设， 实验程序将在已知组成的PU上进行 具有或不具有增强生物稳定性的特定添加剂。 的 拟议研究的具体目标是： 1)为了阐明细胞降解的化学机制 试剂（自由基，HOCl，酸）-引起水解和/或氧化链 聚醚醚酮和其他PU的裂解， 生物降解机制可能不同的部分。 将在加速体外条件下进行相关研究 来模拟体内环境。 2)表征体内和体外后的表面降解 暴露，并将结果与对性能的影响相关联 特性. 材料表征方法将包括衰减 全反射红外光谱，光声红外 光谱，ESCA，接触角，凝胶渗透色谱， 扫描电子显微镜和扫描声学显微镜。 3)确定应力和应变状态对PU速率的影响 生物降解 单轴和双轴应变的影响将是 在体内和体外进行检查，结果将与 蠕变和疲劳行为， 水解条件 4)为了确定PU表面化学的影响以及 对多形核白细胞粘附的添加剂， 单核细胞/巨噬细胞在静态和动态条件下， 而不存在补体。 这些研究将相互关联 通过体内实验来检查抗氧化剂的作用， 巨噬细胞抑制剂的生物降解。

The combination of outstanding physical and chemical properties of polyurethanes (PUs) coupled with their biocompatibility have led to their use in a wide range of biomedical applications. In the last decade, concerns regarding the biostability of PUs were raised when some PU pacemaker leads were shown to undergo environmental stress-cracking in humans. Current studies in this laboratory directed toward a fundamental understanding of biocompatibility and biostability of PU elastomers have led to a hypothesis for the cell/polymer feedback control of in vivo biodegradation. In order to confirm and/or modify the hypothesis, experimental procedures will be carried out on PUs of known composition with and without specific additives that enhance biostability. The specific aims of the proposed research are: 1) To elucidate the chemical mechanisms by which cellular degrading agents (radicals, HOCl, acid)- cause hydrolytic and/or oxidative chain cleavage of polyetherurethanes, and other PUs with non-polyether soft segments where the mechanism(s) of biodegradation may be different. Correlative studies will be made with accelerated in Vitro conditions that mimic the in Vivo environment. 2) To characterize the surface degradation after in Vivo and in Vitro exposure, and correlate the results with the effect on performance properties. Methods of material characterization will include attenuated total reflectance infrared spectroscopy, photoacoustic infrared spectroscopy, ESCA, contact angle, gel permeation chromatography, scanning electron microscopy and scanning acoustic microscopy. 3) To ascertain the effect of stress and strain state on the rate of PU biodegradation. The effects of uniaxial and biaxial strain will be examined in vivo and in vitro, and the results will be correlated with creep and fatigue behavior as determined in vitro under oxidative and hydrolytic conditions. 4) To determine the effect of PU surface chemistry and the effect of additives on the adhesion of polymorphonuclear leukocytes and monocytes/macrophages under static and dynamic conditions, with and without the presence of complement. These studies will be correlated with in vivo experiments to examine the effects of antioxidants and macrophage inhibitors on biodegradation.